Riboflavn の理化學的性質に關する研究 (第5報) : Paper Chromatography による光分解經過の追跡
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It is known that the main photo-decomposition products of riboflavin are lumiflavin in alkaline side and lumichrome in acidic side. But it is not clear by what processes theses subststances are produced.In order to clarify the decomposition mechanism, the present author attempted to apply the paper chromatography for the separation and identification of riboflavin and related decomposition products formed by light destruction on vairous conditions.In the present study, the samples of solutions exposed to light were spotted on Toyo No.2 filter paper strips 2×50cm. The chromatograms developed with the upper layer of mixture of n-butanol-acetic acid-water (4 : 1 : 5) had several fluorescent spots under illuminating ultra-violet ray.When the samples were exposed to 100 W. artificial lamp at 20 cm distance in the alkaline medium, the intensities of fluorescence were as following : The spot with yellow fluorescence and Rf 0.35〜0.39 (riboflavin) disappeared slowly. The spot with yellow fluorscence and Rf 0.47〜0.54 (lumiflavin) became distinct gradually, but was apt to become weak again after 2 hours. The spot with blue fluorescence and Rf 0.68〜0.75 (lumichrome) and the spot with yellow fluorescence and Rf 0.24〜0.30 (unidentified substance) were observed to be almost constant; but still more faint. Sometimes, the other several weaker unidentified spots appeared between 0.04 and 0.20 of Rf.On the other hand, when exposed in acidic medium, the disappearance of the spot of riboflavin was more slow and the intensities of fluorescence of the spots of lumichrome (stronger), lumiflavin (weaker) and the others (weaker) were nearly constant.It was found that riboflavin was more stable to light in acidic side than in alkaline side and that lumiflavin, lumichrome and the unidentified substance with Rf 0.24〜0.30 were formed in almost all pH range. Perhaps, the last substance seems to be one of the main photo-decomposition products, too.Whether this substance is the product to which lumiflavin or lumichrome is further decomposed, or the intermediate product which is decomposed to lumiflavin or lumichrome, is under investigation.When the samples were heated during exposure, the new spot with deep bluw fluorescence and Rf 0.50〜0.55 appeared in alkaline side and, moreover, the rata of decomposition was very large. In this case, the reaction mechanism seems to be different from the one without heating.
- 1951-01-15
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